<html lang="en">

<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>Document</title>
  <!-- 引入样式 -->
  <link rel="stylesheet" href="https://unpkg.com/element-ui/lib/theme-chalk/index.css" />
  <!-- 引入组件库 -->
  <script src="https://unpkg.com/element-ui/lib/index.js"></script>
  <style lang="css">
    .box {
      height: 200px;
      display: flex;
    }

    .box-item {
      height: 100px;
      width: 200px;
      background-color: pink;
    }

    .box-item:nth-child(2) {
      background-color: rgb(0, 255, 115);
    }
  </style>
</head>

<body>
  <div class="box">
    <div class="box-item"></div>
    <div class="box-item"></div>
    <div class="box-item"></div>
  </div>
</body>

</html>